The logic model may be hierarchical (that is,
consisting of macro building blocks), or flat (that is, a single level of
hierarchy with no macro building blocks). Hierarchy does not impose structures on lines; for example, there is no implied fan-out origin at a macro input or output. Macros that correspond to physical partitions in a model shall use additional buffers (or an equivalent method) to enforce adherence to the actual DUT's fan-out.